Color television is ordinarily transmitted by means of a set of video signals comprising a luminance signal and two signals that are vector components of the chrominance. The copending application Ser. No. 354,138 now U.S. Pat. No. 4,568,966 and related U.S. Pat. Nos. 4,275,411 and 4,460,924 disclose color-television transmission with at least one of said video signals dither-quantized according to very coarsely quantized samples. The related patents disclose various digital and other systems for transmitting the information of said samples while the copending application has particular reference to systems transmitting a signal that remains compatible with NTSC receivers or other analog receivers. The aforementioned disclosures also include embodiments applicable to video recording and means for television encryption.
This application concerns color television systems that send color information in terms of dither-quantized samples corresponding to only a few discrete chrominance values and use 3-dimensional dithers that allow substantially normal pictures to be perceived. All references herein to the copending application refer to my application Ser. No. 354,138 now U.S. Pat. No. 4,568,966.
For purposes of this application, chrominance is defined as the vector sum of two chrominance components (typically I and Q or R-Y and B-Y) in quadrature. A point of the I-Q plane represents a particular value of the chrominance vector (I,Q). The same vector may be written (H,S) in polar coordinates, where H is the polar angle corresponding to hue and S is the polar distance corresponding to chrominance amplitude. Point (0,0), the origin of both Cartesian and polar coordinates, is the "neutral point" associated with zero (or neutral) chrominance, found in black, white and gray picture details. The color subcarrier used in the NTSC system of color television is quadrature-modulated so that its phase is the analog of H and its amplitude the analog of S.